exfat: retain 'VolumeFlags' properly

MediaFailure and VolumeDirty should be retained if these are set before
mounting.

In '3.1.13.3 Media Failure Field' of exfat specification describe:

If, upon mounting a volume, the value of this field is 1,
implementations which scan the entire volume for media failures and
record all failures as "bad" clusters in the FAT (or otherwise resolve
media failures) may clear the value of this field to 0.

Therefore, We should not clear MediaFailure without scanning volume.

In '8.1 Recommended Write Ordering' of exfat specification describe:

Clear the value of the VolumeDirty field to 0, if its value prior to
the first step was 0.

Therefore, We should not clear VolumeDirty after mounting.
Also rename ERR_MEDIUM to MEDIA_FAILURE.

Signed-off-by: Tetsuhiro Kohada <[e-mail]>
Signed-off-by: Namjae Jeon <[e-mail]>

fs/exfat/exfat_fs.h

···
 	unsigned int num_FAT_sectors; /* num of FAT sectors */
 	unsigned int root_dir; /* root dir cluster */
 	unsigned int dentries_per_clu; /* num of dentries per cluster */
-	unsigned int vol_flag; /* volume dirty flag */
+	unsigned int vol_flags; /* volume flags */
+	unsigned int vol_flags_persistent; /* volume flags to retain */
 	struct buffer_head *boot_bh; /* buffer_head of BOOT sector */
 
 	unsigned int map_clu; /* allocation bitmap start cluster */
···
 }
 
 /* super.c */
-int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag);
+int exfat_set_volume_dirty(struct super_block *sb);
+int exfat_clear_volume_dirty(struct super_block *sb);
 
 /* fatent.c */
 #define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu)

fs/exfat/exfat_raw.h

···
 
 #define EXFAT_MAX_FILE_LEN	255
 
-#define VOL_CLEAN		0x0000
-#define VOL_DIRTY		0x0002
-#define ERR_MEDIUM		0x0004
+#define VOLUME_DIRTY		0x0002
+#define MEDIA_FAILURE		0x0004
 
 #define EXFAT_EOF_CLUSTER	0xFFFFFFFFu
 #define EXFAT_BAD_CLUSTER	0xFFFFFFF7u

fs/exfat/file.c

···
 	if (ei->type != TYPE_FILE && ei->type != TYPE_DIR)
 		return -EPERM;
 
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 
 	num_clusters_new = EXFAT_B_TO_CLU_ROUND_UP(i_size_read(inode), sbi);
 	num_clusters_phys =
···
 	if (exfat_free_cluster(inode, &clu))
 		return -EIO;
 
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 
 	return 0;
 }

fs/exfat/inode.c

···
 	if (is_dir && ei->dir.dir == sbi->root_dir && ei->entry == -1)
 		return 0;
 
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 
 	/* get the directory entry of given file or directory */
 	es = exfat_get_dentry_set(sb, &(ei->dir), ei->entry, ES_ALL_ENTRIES);
···
 	}
 
 	if (*clu == EXFAT_EOF_CLUSTER) {
-		exfat_set_vol_flags(sb, VOL_DIRTY);
+		exfat_set_volume_dirty(sb);
 
 		new_clu.dir = (last_clu == EXFAT_EOF_CLUSTER) ?
 				EXFAT_EOF_CLUSTER : last_clu + 1;

fs/exfat/namei.c

···
 	int err;
 
 	mutex_lock(&EXFAT_SB(sb)->s_lock);
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 	err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_FILE,
 		&info);
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 	if (err)
 		goto unlock;
 
···
 	num_entries++;
 	brelse(bh);
 
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 	/* update the directory entry */
 	if (exfat_remove_entries(dir, &cdir, entry, 0, num_entries)) {
 		err = -EIO;
···
 
 	/* This doesn't modify ei */
 	ei->dir.dir = DIR_DELETED;
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
···
 	int err;
 
 	mutex_lock(&EXFAT_SB(sb)->s_lock);
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 	err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_DIR,
 		&info);
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 	if (err)
 		goto unlock;
 
···
 	num_entries++;
 	brelse(bh);
 
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 	err = exfat_remove_entries(dir, &cdir, entry, 0, num_entries);
 	if (err) {
 		exfat_err(sb, "failed to exfat_remove_entries : err(%d)", err);
 		goto unlock;
 	}
 	ei->dir.dir = DIR_DELETED;
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
···
 	if (ret)
 		goto out;
 
-	exfat_set_vol_flags(sb, VOL_DIRTY);
+	exfat_set_volume_dirty(sb);
 
 	if (olddir.dir == newdir.dir)
 		ret = exfat_rename_file(new_parent_inode, &olddir, dentry,
···
 		 */
 		new_ei->dir.dir = DIR_DELETED;
 	}
-	exfat_set_vol_flags(sb, VOL_CLEAN);
+	exfat_clear_volume_dirty(sb);
 out:
 	return ret;
 }

fs/exfat/super.c

···
 	/* If there are some dirty buffers in the bdev inode */
 	mutex_lock(&sbi->s_lock);
 	sync_blockdev(sb->s_bdev);
-	if (exfat_set_vol_flags(sb, VOL_CLEAN))
+	if (exfat_clear_volume_dirty(sb))
 		err = -EIO;
 	mutex_unlock(&sbi->s_lock);
 	return err;
···
 	return 0;
 }
 
-int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
+static int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flags)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
 	bool sync;
 
+	/* retain persistent-flags */
+	new_flags |= sbi->vol_flags_persistent;
+
 	/* flags are not changed */
-	if (sbi->vol_flag == new_flag)
+	if (sbi->vol_flags == new_flags)
 		return 0;
 
-	sbi->vol_flag = new_flag;
+	sbi->vol_flags = new_flags;
 
 	/* skip updating volume dirty flag,
 	 * if this volume has been mounted with read-only
···
 	if (sb_rdonly(sb))
 		return 0;
 
-	p_boot->vol_flags = cpu_to_le16(new_flag);
+	p_boot->vol_flags = cpu_to_le16(new_flags);
 
-	if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->boot_bh))
+	if ((new_flags & VOLUME_DIRTY) && !buffer_dirty(sbi->boot_bh))
 		sync = true;
 	else
 		sync = false;
···
 	if (sync)
 		sync_dirty_buffer(sbi->boot_bh);
 	return 0;
+}
+
+int exfat_set_volume_dirty(struct super_block *sb)
+{
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	return exfat_set_vol_flags(sb, sbi->vol_flags | VOLUME_DIRTY);
+}
+
+int exfat_clear_volume_dirty(struct super_block *sb)
+{
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	return exfat_set_vol_flags(sb, sbi->vol_flags & ~VOLUME_DIRTY);
 }
 
 static int exfat_show_options(struct seq_file *m, struct dentry *root)
···
 	sbi->dentries_per_clu = 1 <<
 		(sbi->cluster_size_bits - DENTRY_SIZE_BITS);
 
-	sbi->vol_flag = le16_to_cpu(p_boot->vol_flags);
+	sbi->vol_flags = le16_to_cpu(p_boot->vol_flags);
+	sbi->vol_flags_persistent = sbi->vol_flags & (VOLUME_DIRTY | MEDIA_FAILURE);
 	sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
 	sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
 
···
 		exfat_err(sb, "bogus data start sector");
 		return -EINVAL;
 	}
-	if (sbi->vol_flag & VOL_DIRTY)
+	if (sbi->vol_flags & VOLUME_DIRTY)
 		exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");
-	if (sbi->vol_flag & ERR_MEDIUM)
+	if (sbi->vol_flags & MEDIA_FAILURE)
 		exfat_warn(sb, "Medium has reported failures. Some data may be lost.");
 
 	/* exFAT file size is limited by a disk volume size */